Was−/− B cells exhibit high levels of antigen-dependent clonal expansion. (A) 8–10-wk-old WT (n = 7), Was−/− (n = 9), and Wasfl/fl × Mb-1Cre (n = 6) mice were treated with BrdU in vivo for 24 h. BM and splenic B cell subsets were analyzed for BrdU incorporation via FACS. Data are representative of one of three experiments (WT, n = 3; Was−/−, n = 3; Wasfl/fl × Mb-1Cre, n = 3). (B) Cell cycle analysis of splenic B cell subsets via DAPI labeling in 8–10-wk-old WT (n = 7), Was−/− (n = 9) and Wasfl/fl × Mb-1Cre (n = 6) mice. (C) Serum BAFF levels in WT (n = 11), Was−/− (n = 9), and Wasfl/fl × Mb-1cre (n = 6) mice. (D) Representative data showing GFP staining of splenic T1 (left) and T2 (right) B cells in WT and Was−/− Nur77 Tg mice. (E and F) Percentage of GFPhi and GFPlo T2 B cells (E) and MFI of GFP in B cell subsets (F) in WT and Was−/− Nur77 Tg mice (n = 8/each). (G) Percentage of BrdU+ T2 GFPhi and GFPlo cells in WT (n = 7) and Was−/− Nur77 Tg (n = 6) mice. (G and H) 8–10-wk-old WT M167 Tg (n = 5) and Was−/− M167 Tg mice (n = 5) were treated with BrdU in vivo for 24 h. (H) Representative contour FACS plot showing BrdU incorporation in WT (top) versus Was−/− (bottom) M167 (Id)+ T2 B cells. (I) Percentage of M167 Id+Ki-67+ and Id−Ki-67+ splenic T2 B cells in WT (n = 5) versus Was−/− M167 (n = 6) Tg mice. Error bars show SEM. Statistical analysis was performed using the Student’s t test: *, P < 0.05; **, P < 0.01; ***, P < 0.001. Data are representative of at least two experiments.